A friend convinced me to go in with him on a 5D Tactical jig & I built way too many AR's, I find the standard .223/5.56 are very easy to build and usually work the very first time I take them to the range-- Then I started building the AR-9,AR-10, AR-45 and they need more tweaking to make them work right. Now I have way too many AR's in every caliber I like